{Chrysler 300} Taper brake drums and F plate frame —— FYI

[John Grady <jkg@xxxxxxxxxxxxxxxxx>]

Trying now for 3 months now on and off car to get new manufacture uncut drums correctly centered to our stock taper rear hubs . There are no pilots , the thing was apparently machined in one piece at factory to center shoe surface to taper . —and new drum stud holes are oversize compared to our old ones cannot do the common ( today ) press fit stud way of centering drum without major machining of  hub for new very large studs . Which may lose center precision  . Not that good to start , per measuring all  5 , was  only intended to hold wheel ? Conical bolts average it out? 
Drum center “new style pilot hole  “ are about 2” used on new drums to center but 2” drum machining hole is  tapered inside , you need to take like 3/16” off our hub face to make a deep enough pilot -that is too much . Hub flange is not very thick ( ? safety issue )  .
Frustrating thing , 3rd time all four off the car . This time We bought real brake drum arbors and shaft/ cones ; but with taper hubs there are real issues with trueness of taper inlet and outlet diameters where drum turning cones sit . Normal cones were  too large for small outer end of taper , we had to buy a whole second set and smaller arbor made for euro small cars . Days of messing with this trying to get consistent numbers in lath setup leads to conclusion our drums were allowed to be slightly wobbling ( -.010 -.015) as rough attached to hub , and this was fixed if it happened by final machining of “shoe face inner  12” cylinder “ referencing to only the taper . So 11or 12” “ bore”” is often moving around some , inside  the stock casting , —-= why most original drums on our cars have factory welded balance weights . You take this apart you are screwed , cannot get good radial numbers due to slight  wobble  . New drums do same thing . Our concept was simple — hand center drum radially on hub then pin , wheel clamp force is holding then too  it looks like later no taper mopar . Simple thing has turned into atomic project , radial numbers all over the place partially due to wobble . 

Add in doubts about real cause of measured weird runouts -? = It is a 3D issue ?? due to cones sitting on taper ends not in the plane of drum face , leads to inescapable conclusion we need to make a tool  out of a used axle to hold the hub for sure on intended center, and be truly orthogonal to axle .  . As they must have done . So this long story is asking if anyone has a junked rear or loose axle . We will pick up shipping . I trashed many rears , someone must have a junk one out back , or axle . Clean up the yard!! Wrecking yards won’t ruin a full assembly . All axle ends seem the same plymouth to 300 , 11 and 12 “ .

We need to solve this as drums “already on taper hubs”  (as mopar serviced this ) are not available new  and used are topping 350 and often already cut to max. New drums sold by Kanter for instance have oversize bolt  holes do not center without a pilot . How this started , inherited from prior owner who gave up 


Second —- back at F plate frame , — we could use the center part cut out of junk 60 body below trunk  where plate frame mounts so fabrication house can trial fit , use for QC . 3 rd try at this one , back to brass casting . Twenty years and 5k later ( plastic injection molds — parts were failure cannot chrome well)  still no good  F frame . Help on this appreciated !
Best regards ,and thanks  John Grady 

Sent from my iPhone

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